Genes and Genetic codes

• Label the structure

  A) chromosome

  B) telomere

  C) centromere

  D) chromatid

  E) supercoiled

  F) gene

  G) DNA double helix

  H) Base pair

  
• Homologous chromosomes contain DNA that codes from the same gene. The alternate forms of the same gene is called an allele. Sister chromatids are exact replicas. Both chromosomes have all the same genes in the same locations but different 'versions' of those genes. A section of DNA at a particular position is called a locus
• The human genome is about 3.2 billion base pairs long. this is the length of all the DNA in a humans cells, which is packaged into 46 chromosomes in the nucleus. If you stretched out all the DNA in a single cell it would be about 2 meters long. The DNA in all of a persons cells would be long enough to wrap around the earth-sun distance more than 41 times
• DNA and Histones


  DNA is wrapped around histone proteins, which are positively charged proteins that adhere to the negatively charged DNA. This forms nucleosomes, which are bead-like units that are the basic level of chromosome organisation
• Chromatin


  Nucleosomes coil together to form chromatin which is a fibre with a diameter of about 30 nanometers
• Chromosomes


  Chromatin loops and folds with the help of additional proteins to form chromosomes
• Order of how DNA fit into a nucleus

  1. DNA and Histones
  2. Chromatin
  3. Chromosomes
• Is all DNA packaged in the same way?

  • In prokaryotic cells, DNA molecules are short, circular and not associated with proteins.
  • The mitochondria and chloroplasts of eukaryotic cells also contain DNA which, like the DNA of prokaryotes, is short, circular and not associated with protein
• Gene


  • a base sequence of DNA that codes for:

  1. the amino acid sequence of a polypeptide
  2. or a functional RNA including tRNA and rRNA

  A gene occupies a fixed position, called a locus, on a particular DNA molecule
• The Genetic Code


  • a sequence of 3 DNA bases called a triplet codes for specific amino acids
  • there are only 20 regularly occuring amino acids
  • each amino acid must have its own code
  • only 4 bases in DNA
  • If each base = 1 amino acid, that would be be 4 amino acids coded for
• Bases and amino acids

  A) w

  B) T

  C) X

  D) C

  
• The genetic code


  • There are only 20 regularly occurring amino acids
  • Each amino acid must have its own code
  • only 4 bases in DNA
  • If 2 bases = one amino acid still only give 16 different codes
• why is the genetic code describes as being universal


  in all organisms the same triplet codes for the same amino acid
• The genetic code uses 4 different DNA bases. whis is the max number of different DNA triplets that can be made using 4 bases?


  64
• Label

  A) supercoiled DNA

  B) Chromosome

  C) chromatin fiber

  D) DNA and Histones

  E) DNA double helix